Charls:
It depends on age and storage conditions.
Since it's Kynoch, it will be date coded. From 1926, this was stamped on the back of the box as a number followed by two letters, such as "7 M U" (day, month, year), so aging it precisely is easy. What is the date code? Is the box marked "Imperial Chemical Industries"/"ICI", or "Imperial Metal Industries"/"IMI"? Given the caliber, I assume it will be ICI, rather than IMI. What color is the box? I'll be happy to date it for you.
I agree that original ammo in that caliber would likely be too valuable to shoot, which would also mean you shouldn't pull the bullets and reload the cases. If the ammo is original to the boxes, it will be Berdan primed anyway. You'd be better off buying new Boxer cases and reloading.
